A novel atomic layer deposition process of manganese oxide from methylcyclopentadienyl manganese tricarbonyl and ozone has been developed. It is used to coat vertically aligned carbon nanotubes (VACNTs) grown on a conductive Inconel substrate in order to produce a 3D array of metal oxide-carbon nanotube electrode. Electron microscopy studies show that a conformal polycrystalline film can be deposited on the VACNTs arrays. X-ray diffraction, small area electron diffraction, and X-ray photoelectron spectroscopy analysis determine the formation of hausmannite (Mn3O4). The electrochemical properties of the as-prepared VACNTs/Mn3O4 nano-composite electrodes are studied using cyclic voltammetry, galvanostatic charge and discharge cycling in 1 m Na2SO4 aqueous electrolyte. Capacitances as high as 78.62 mF cm(-2) at 5 mV s(-1) are demonstrated which is one order of magnitude higher than that of pristine VACNTs. In addition, the as-prepared VACNTs/Mn3O4 nanocomposite electrode showed a good reversibility and cycling stability.